At ejaculation, greater than 99% of the potential boar acrosin (EC 3.4.21.10) is present as an enzymatically inactive zymogen precursor, proacrosin. Since sperm require enzymatically active acrosin to penetrate the zona pellucida of an ovum, the proacrosin must be converted to acrosin before the sperm can achieve the capacity to fertilize. The primary objectives of this proposal are to continue our investigations of the molecular mechanisms of proacrosin conversions to acrosin and to characterize the regulation of this conversion. A multidisciplinary approach to the problems will utilize highly purified boar proacrosin to: a) biochemically characterize the protein, i.e., amino acid and carbohydrate composition, terminal amino acid analysis, etc.; b) determine the possible molecular mechanisms of proacrosin; c) isolate and characterize uterine fluid factors which stiumlate this conversion; d) isolate and characterize a sperm factor that inhibits the conversion; e) develop and synthesize synthetic inhibitors to proacrosin; f) investigate the properties of membrane bound proacrosin through the use of a phospholipid bilayer vesicle model membrane system; and h) raise antibodies to both proacrosin and the proacrosin conversion peptides then determine if the antibodies can bind to and inhibit membrane bound proacrosin as well as determine the cross species specificity of the antibodies. Intact sperm will also be utilized to determine if the proacrosin conversion stimulators and inhibitors have biological effectiveness by affecting proacrosin within the sperm and can therefore influence fertilization.